1. Field of the Invention
The present invention relates to a method of generating data for use in monitoring and controlling the charge and discharge status of a secondary battery, and more particularly, to a method of generating data, by a microcomputer installed in a secondary battery pack and transferred to an external device.
2. Description of the Related Art
The advent of portable electronic devices such as notebook computers, camcorders and cellular phones has enabled the development of secondary batteries. In order to recharge a secondary battery, data for use in accurately monitoring and controlling the charge and discharge status of the secondary battery are required. Also, because a reference full-charge capacity, which is essential to calculate the data, substantially changes over time, is necessary to periodically monitor and update the reference full-charge capacity to generate such data.
For this reason, secondary battery packs have adopted a microcomputer and a peripheral circuit for generating data used to monitor and control the charge and discharge status. In a conventional algorithm programmed in the microcomputer, which is installed in the secondary battery, the reference full-charge capacity of the secondary battery is periodically updated through a learning process performed during charging of the secondary battery. That is, the conventional algorithm calculates a real full-charge capacity, which is proportional to the rate of charging of the secondary battery, and designates the calculated real full-charge capacity as a reference full-charge capacity.
However, since the charging properties of the secondary battery do not abruptly change over time, the algorithm performed by a microcomputer installed in the conventional secondary battery pack cannot be considered as a good algorithm which well reflects the operating properties of secondary batteries. Thus, the degree of accuracy in data associated with the reference full-charge capacity is lowered. In addition, the conventional algorithm determines the charging voltage value using only a read instantaneous voltage value, thereby further lowering the accuracy of data.
An object of the present invention is to provide a method of generating data for use in monitoring and controlling the charge and discharge status of a secondary battery, in which the operating properties of the secondary battery are accurately reflected.
In an aspect of the present invention, there is provided a method of generating data for use in monitoring and controlling the charge status and discharge status of a secondary battery, which is performed by a microcomputer installed in a secondary battery pack, the method comprising: periodically calculating and updating an average voltage value xe2x80x9cadadvolxe2x80x9d of the secondary battery; selecting and executing a charge mode, a discharge mode, a self-discharge mode according to the amplitude and sign of an instantaneous current xe2x80x9cadcurxe2x80x9d flowing through the secondary battery; when the discharge mode is iteratively performed, periodically calculating discharge capacity xe2x80x9cDCRxe2x80x9d and updating a required full charge capacity xe2x80x9cs_dcrxe2x80x9d with the calculated result; and if the average voltage value xe2x80x9cavadvolxe2x80x9d for the present period of time drops below a lower limit of a full discharge voltage value xe2x80x9cs_edv0xe2x80x9d, updating a reference full charge capacity xe2x80x9cf_c_capacxe2x80x9d with the required full charge capacity xe2x80x9cs_dcrxe2x80x9d.
In the data generating method according to the present invention, the reference full charge capacity xe2x80x9cf_c_capacxe2x80x9d is updated with the required full charge capacity xe2x80x9cs_dcrxe2x80x9d obtained in a discharge mode. That is, the discharging properties of the secondary battery, which, in contrast to the charging properties, sharply change with time, are reflected in the reference full charge capacity xe2x80x9cf_c_capacxe2x80x9d, so that the charge status and discharge status of the secondary battery can be monitored and controlled with accurate data. Also, the charge status of the secondary battery is determined using the average voltage value of the secondary battery, and thus more accurate data can be generated.